Abstract

Abstract

The water factor's role in sprouting was defined for intact mature hard red spring wheat (Triticum aestivum L.) spikes in laboratory experiments as a prelude to developing a sprouting model. Grain and spike water concentration are essentially synonymous at harvest ripeness. Spike water concentration increased linearily by 10 g kg−1 min−1, dry wt at 69°C, when continuously misted at 19 mm h−1, while water imbibition by grain in once wetted intact spikes increased curvilinearily, varying with spike water concentration and equilibration time. Maximum imbibition rate of grain was 17 g kg−1 h−1 with wheat spike water concentration at 1450 g kg−1. Water evaporation from wetted spikes was slower at high than low relative humidity, and slower after equilibration (time for imbibition) than if drying was initiated immediately after wetting. Minimum equilibrated spike water concentration inducing sprouting was about 450 to 490 g kg−1. Sprouting was not induced by wetting field-growing wheat during primary dehydration until the water concentration had declined to about 120 g kg−1 for at least 2 days. When cut at Feekes stage 11.3, the number of drying days required before any sprouting could be induced varied with cultivars, ranging from about 4 to more than 15 days. Sprouting potential was enhanced by wetting-drying cycles in which the wetted interval was too brief to permit sufticient imbibition to initiate sprouting. Ninety percent of the kernels in 300 mature spikes sprouted within 8 days after misting to saturation (about 1500 g kg−1 water contmtration) and maintained at a minimum of 750 g kg−1; 20% of the kernels sprouted within 28 h of initiation of wetting.

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